PHP 5 is a bugger to install on WS2K3. Try checking to make sure PHP 5 is installed properly.
For example, make a file named test.php, open it in notepad and add the following:
<?php phpinfo(); ?>
Copy it to the root web folder and open it in a web browser. (eg. http://localhost/test.php(http://localhost/test.php))
If you get a blank page or an error, PHP is not setup corectly.
I recommend these tutorials:
http://www.tjitjing.com/blog/2006/05/php5-with-iis6-on-windows-server-2003.html(http://www.tjitjing.com/blog/2006/05/php5-with-iis6-on-windows-server-2003.html)
http://www.peterguy.com/php/install_IIS6.html(http://www.peterguy.com/php/install_IIS6.html)
Remember PHP setup on WS2K3 is not the easiest thing to figure out for first-timers. Hopefully those will help you.
Edit: I recommend manual installation opposed to the auto installer on php's homepage.